Ever walk down a beach and find yourself in wonder, about the mysterious artist who creates these amazing sand balls designs?
Well, on your next trip to the shore, just below the high water line, try and spot an evasive little crab, measuring about a centimeter across, called the “Sand Bubbler Crab”. With an exoskeleton, the same color as the sand, these seaside Picassos are easy to miss.
What’s unmissable however are the intricate patterns they make on the beach when they search for food. Like tiny galaxies, these patterns are composed of hundreds of tiny sand balls — sometimes thousands, depending on how many fellows were snacking.
These tiny crustaceans of the genera Scopimera and Dotilla in the family Dotillidae, a family of crabs that contains 59 species, have spherical bodies with long and flat pinchers, hairy legs, and eyes on short stalks which can fold away into grooves when the crabs scurries into its burrow.
The sand bubbler crab eats the thin coating of edible organic particles on sand grains. When the tide goes out, the crab emerges from their burrows and starts sifting through the sand, picking up the sand grains with their downward-pointing pincers and bringing it to their mouth to scrap the microscopic food. After they have scrapped the sand grains clean, they roll them into little balls and toss them behind. By doing this they avoid sifting the same sand twice.
Making sand balls is easier said than done when you’re a delicious crab dashing across a beach frequented by hungry birds. While their calcified exoskeleton is well camouflaged, they can still be spotted when rolling their balls and so an easy exit strategy is vital to survival. As such, they work in a pattern that can resemble a star or a spiral, with a clear runway back to their central burrows should any suspect characters approach. It’s yet another example of how evolution results in patterns in nature that look as if they’ve been crafted by an artist but are just happy accidents.
The feeding activity continues till the high tide comes. During high tide, the balls get washed away and the sea waves replenish the sand with micronutrients. When the high tide subsides, crabs come out to start the process all over again. You can almost tell how long the tide has been out by the patterns of their sand balls. The more intricate the pattern of sand balls, the longer the tide has been out. What’s fascinating about the crabs’ gorgeous sand artwork is that because it’s washed away with each incoming tide, it’s inherently ephemeral — making it all the more special to observe.
These crabs widely seen along the sandy beaches of Goa are facing imminent threats as the beach is getting continuously polluted due to boats’ oil spillage, which eventually triggers habitat loss. The disturbed ecological niche will subsequently hamper the food chain as well as harmonious living of these tiny creatures.
Next time you walk along the sandy beach, look for these intricate patterns of balls. Capture their dedicated work and watch the video on a stressful day. It can be quite a stress-buster!
The below video was shot by me on my phone at Zalor beach this evening, its original time is 15 minutes, I have sped it up to 45 seconds.
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